1 Bad Mirada

im making around 500bhp with a pushrod motor, with 2 (very small) valves per cylinder....on 87 octane. 12.40s in a 3700lbs car.

i believe that pretty much every NHRA class is using a pushrod setup.

Blackflag

That's cool, thanks for remembering me. I'm flattered. First, I don't want to see the new hemi go 4 valves. I don't care much where it goes, I was just correcting the point that 4 valves hurt fuel economy. Second, the 426 is a legendary engine that I've been enamoured with for a long time. There are very few designs in the world that are as impressive. And I love the pushrod setup on that engine. (but I'm not really a fan of cam/poppet valve at all) If this were 1963, the "new" hemi would be an awesome engine. Unfortunately, this is 2007, and in the world of engines, it's just a tad lame. Sorry if that hurts anybody's feelings, but I gotta be me.

Thanks for the background, I'm not that familiar with the large car engines. The problem with your argument, though, is that the 3.5l gets worse fuel economy because ... it has a higher displacement. The 5% difference in displacement just about accounts for your difference in fuel economy. So it's kind of hard to make any determination about the contribution from the 4 valves.

The only thing I really know about the quad 4 is that it was supposed to be their "performance" version. See, that's the thing. If you want to put on 4V, then cam it for performance...sure you'll get better performance and worse fuel economy. But that's a tradeoff decision, not the fault of 4V.

There are plenty of examples, but I can't go dig them up. I think the 1G Neon got the same fuel economy for both engines, which is a tradeoff of fuel economy for better performance. A better place to look is the European engines, where fuel economy is favored. I don't even think you can buy a 2V in Europe - what does that tell you?

The bottom line is this - if you take the same engine, same displacement, same cam, and run it on a dyno with a 2V configuration then a 4V configuration, the 4V is more efficient. This discussion is cool - I do this for a living, so I could talk about it all day - but that point isn't really open to debate. You can find it in a basic book, I think kids in college even learn the point.


[quote]ORIGINAL: RLSH700
Out of all of the different car companies in the world, the last two I would ever use as a benchmarker or one to follow the example of are Mercedes and Ford. The Modular 3 valve engine are not very efficient, nor very powerful despite the modern technology added to them. The Hemi blows the Modular out of the water in terms of power in the truck line and the 6.1L Hemi has more hp per cubic inch than the 4.6L Modular. Do I even have to start on Mercedes? With the exception of their diesels, they are not fuel mileage benchmarkers either. The best they can do with a V8 is 24 mpg and that is with a 7-speed auto with a 2.65 axle ratio (combin

lear4406

The answer to " Does Chrysler have a V-8 engine that gets 24 mpg" yes, yes they do. My son has a Charger Daytona 5.7. And yes it does get 24 mpg. Thats usually with me driving it. Chrysler does things with their push rod engine that an over head cam 4 valve cannot do. Multiple Displacment. I like overhead cams and 4 valves per cylinder. But I'm not ready to throw in the towel on the push rod engines yet. There is more than one way to skin a cat ( kind of gross if you think about it). We don't have to follow Europes lead on cars, I could give a good rats... butt what they do with their cars. I like the Hemi and as a Child of the 60's, I waited more years than I care to remember, to own a new HEMI car. Its taken until recently to get to this point. Its been an evolution so to speak. I went through the 80s and most of the 90s with no glimmer of hope. Now we have a chance to own a little Americana. By chance do you watch the LeMans series and have you seen over the last few years when American cars compete head to head with an European car in the same class. We more than likly end up on top. Viper and Corvette come to mind. Yeah ... you guessed it, push rod 2 valve. Kicking butt and taking names, like Jag, Ferrari, Porche, ect. You also have to remember. 24 hours is an endurance race also as well as horsepower. The more valves you have the more chance you have to burn one. Don't sell American technology short. 4 valves per cylinder has volumetric efficency no doubt. But when you want to be top dog... the pushrod rules for now. Top fuel is a good example. They could run any motor they want, but its the old style 60's HEMI that they build around. Talk about vol. eff. Put a turbo or a blower on a HEMI and you run the show... no ifs ands or buts about it. Will it always be that way? Who knows... only time will tell.

RLSH700

Your argument is still flawed. You said that added 4 valves per cylinder on the Hemi would help the fuel economy in a 7.0L version which is an increase from the current sizes as well; therefore, make up your mind. Whether it will improve the economy or not.

Next about the 3.3L to 3.5L argument being displacement, what about the case of the Chrysler Pacifica? In the first generation offerings, they offered the 3.8L OHV (which is just a larger version of the 3.3L OHV) and the 3.5L SOHC with the same transmission and gearing; however, the LARGER 3.8L OHV was rated at getting 25 mpg on the highway, while the SMALLER 3.5L was only rated at 23 mpg. That disproves your argument that the drop in fuel economy was due to a very slight displacement increase as a DEcrease in displacement did not help the 3.5L in getting better fuel economy. While we are looking at this engine family and platrform, why don't we see how the difference in displacement effected the fuel economy between using the 3.3L and 3.8L engines in the normal minivans. The fuel economy on the 3.3L was 26 mpg while the 3.8L's was the same 25 mpg. Over double the displacement increase made less an effect on the fuel economy than shrinking the displacement and using a 4 valve OHC head. Therefore, I find it hard to believe that the displacement is at complete fault of the fuel economy drop, not to mention again that the higher compression ratio would have helped counter that drop or the fact that according to you it should have "helped" the fuel economy.

About the quad fours, that quad 4 that I compared was not even the 180 hp H.O. version, just the 115 hp vs. the 160 hp. Also on top of that, as you reminded me the Neon was unaffected in fuel economy between the more performance tuned version whether it was the original SOHC vs. DOHC H.O. or the SOHC vs. SOHC H.O. therefore, I don't buy that argument either.

As for the Europe issue, take a look at the non-diesel offerings that come from Europe from just about any brand whatsoever, they get terrible fuel economy for their size. Volkswagen is one of the least efficient manufactures on the market for their displacement and technology. I will slam MB with pride as they are a joke when it comes to fuel economy. Take a look at the gearing for those V8 MB models they have a new 7-speed automatic with the top ratio about a .72-.73 with the axle-ratio of 2.65 can only muster 24 with a 5.5L V8 on the S-Class. In contrast the LT1 powered Impala SS got 26 mpg with only a 3.08 axle ratio with a .70 top gear ratio with the old 4L60E 4-speed; therefore, the Mercedes had the advantage of taller gearing, it had the fuel saving advantage of VVT, it had the compression ratio advantage of 10.7 to 1 vs. 10.0 to 1, it had the advantage of a slightly smaller displacement (5.5L to 5.7L), and still GM still won. Before you argue the weight advantage that the Impala SS had, look up the E-Class which is lighter than either example, it only got 23 mpg (which means I was chosing the example that favored MB). Remember that the LT1 was a Corvette spec engine just adjusted for torque over hp in that version. As lear4406, explained there is a 25mpg Hemi powered Chrysler car. The real question is how these cars would compare if Chrysler had an equal transmission offering (a 7-speed auto with 2.65 axle ratio instead of that left over 5-speed MB unit they had to use on the LX cars).

Also, try to find a gas powered V8 sports car that can get a 28mpg that has the displacement of 6 liters or larger in a 3 or 4 valve configuration from Europe. The old tech LS2 managed to do that in the Corvette and I can't find one that can match that. Or how about a 7 liter that gets 26 mpg?

Most likely the reason why they use 4 valve in Europe is more simply that the engines they are using are so darn small that if you offered them in anything other than 4 valve, they would become underpowered. Also just because they care mo

Blackflag

Again - two 7.0l's (hypothetical) - on a dyno - same engine - same cam - one with 2V, one with 4V...they could reap an FE benefit from the 4V if they wanted to. To make up for the increase in displacement. I don't know how else to say it.

And again...comparing different engine families or different vehicles is really apples and oranges. For example, I'll just point out that the impala is about 3500 lbs and the S Class is about 4500 lbs. Since the MB is ~25% heavier, are you saying the Impala gets 25% better fuel economy? Apples and oranges, but it makes the MB look more impressive, doesn't it?


45 yrs. later. Impressive.

Yeah, true. You can disagree with me, but you can't disagree with a book. Or maybe you can.

I'm pretty sure nobody regulates "smog"...

Ford already has a system on their modular engines, and I think a lot of companies do. It's easier to do on OHC. But I like the rest of Lear's post.

RLSH700

Your problem is your speaking in theories without providing any evidence that proves your theory. I have effectively disproved your theory at this point by provide example after example of how 4 valve OHC switch overs drop in fuel economy. So far the benchmark is 28 mpg on the highway done by a 6 liter OHV, that benchmark has not been exceeded yet.

Not the W-body Impala (which weighs over 3700 pounds BTW), if you know half as much as you claim to know, you would know that my reference to LT1 Corvette spec engine and 4L60E for the powertrain was a reference to the mid-90s Impala SS, not the W-body 5.3L Impala which was originally rated at 28mpg and is still pretty low tech in comparison. It just proves further that despite all the technology upgrades and everything else MB has in its advantage it can't outdo a very low tech car (curb weight was above 4000lbs; meanwhile, the Benz was below 4500 lbs). Besides your complaint about apples to oranges, you provided the challenge, I answered it with the information that was available. Also this was not the heaviest version of these cars the heaviest version (the Cadillac version) weighed 4447 pounds and still achieved 26 mpg. The weight difference between the Mercedes S-Class is a mere 18 pounds.

What is the matter with being able to match an offering using a 56 lower cubic inches without resorting to doubling the number of valves, without using the latest technology (VVT and Direct Injection), using practically the same compression ratio, while having to overcome current regulations that the 426 never had to go through and a lot better fuel mileage and making more affordable for the common man? That is quite noteworthy, not to mention that the 6.1L is no where near the best they have to offer. The new 392 produces a lot more hp & torque than the 426 did in fuel injected form using a very simple FI system, or equal torque and a lot more hp on a more simple carborated system. Also it has been 42 years not 45. If you so deeply love Ford's engines, why don't you just do us all a big favor and just buy a Mustang so then you can have the "high tech" engine with the must have items. Just don't come crying to us when pushrod models kick you high tech behind.

I don't give care about your fear of the environment besides that is not what we are discussing here. There are "experts" on both sides of the issue so don't give me the I'm backed up by experts crap, because so far your backed up by yourself and so far, you have very little credibility.

You complain about the sources I have used against you and the evidence I have used but your problem is you have provided nothing but snide remarks. If you want to debate, then debate, I you just want to be a commentator who does nothing but source himself, then waste someone else's time.

Where have they added a multidisplacement system on the Modular engine? Which model has it? Unless this is in the plan stage somewhere or they have done a pathetic job of making the public aware, they do not have one. I believe you are confused with Variable Camshaft Timing which is NOT a multidisplacement system. If I have to explain what that is to you, someone is really out of his league.

purnrg

Guys why argue everyone is right, 4V engines are more efficient than 2V engines-correct statement, from a point of view. 2v engines are more efficient than 4V engines-correct statement, from a point of view.
The move to 4V overhead cam heads creates an engine that requires less displacement to achieve a certain horsepower (and torque) threshold at a certain (higher) RPM, this is more true in smaller displacement or shorter stroke engines where it is critical to get the mixture into the combustion chamber in a more consistant fashion (OHC engines in general do this better than OHV engines in this application).
A 2V engine is more efficient in larger displacement, longer stroke engines that are required to meet a horsepower (and torque) threshold at a lower RPM (OHV engines in general do this better than OHC engines in this application).
In a nutshell any OHC engine will produce more HP and torque than a similar OHV engine but that HP and torque comes at a higher RPM, so you technically need less displacement to produce the same HP and torque #'s, hence less displacement equals less mixture therefore less fuel but if you want that HP you need to rev the engine higher to get it, at the higher PRM you use more fuel.
An OHV engine will produce its usable HP and torque at a lower RPM so even though the displacement is bigger you rev lower so the engine doesn't use as much fuel.
Both configurations have their advantages and applications, so everyone is right, now go back to dreaming of a cruise in your new Challenger SRT8's with with some good tunes (Black Betty by SOIL is my favorite cruise tune) playing on factory stereo with the 50 Gig Hard drive (for your MP3's). Better yet make plans to meet up somewhere (maybe Montana or Oregon-8 State trooper cars to patrol the entire state) so we can see how fast we can go.

RLSH700

The reason why is he is saying that the displacement should be increased along with doing 4 valve per cylinder with an OHC design will improve the efficiency. So far, it appears that larger displacement OHVs get better power for you dollar both initially and afterwards at the gas pump. The other point is such a move will drive up the cost significantly from where it already is. Plus, he hasn't provided any evidence yet proving any of his points.

Blackflag

Why are you so angry? We're just having a discussion.

I think the mistake you're making is where you say we're "debating." I'm not debating anything. I'm just making a statement, that's pretty well understood. No, I don't have time to research the issue and prove it to you. Plus, it's kind of fruitless to try and find modern vehicles that use two valves to make a comparison. Are there any manufactuers that make a two valve and four valve version of the same engine? Not today, I don't think. And are there any Jap. or Euro. manufacturers who make a 2V at all? Again, I dont' think so. I'm not saying European engines are better, but I'm saying they know how to favor fuel economy.

Plus, I don't even understand your terminology. OHV? Aren't both 2V and 4V OHV..? And pushrods don't have a lot to do with it, because you can have a 4V pushrod engine. It's really a question of 2V vs. 4V. And I don't understand your point about a 6L OHV engine? Again, I can't "prove" anything without taking a lot of time, so I pulled a few cites off the internet. Don't ask me to explain them, because I've already spent way too much time "debating" the obvious here. Thanks.

UC Irvine
http://darwin.bio.uci.edu/~sustain/g...ndhu/fuel.html

"Along the lines of the OHC engine, another modification that can be made to the engine is by having four valves per cylinder. . . . Also, a greater valve area reduces any losses that may have been incurred through pumping, and there is also an increase in compression ratio, leading to a higher thermodynamic efficiency. ...

When compared directly to a two-valve engine with the same cylinders, the four-valve engine has a five percent advantage in fuel economy. The four-valve engine has an eight percent margin in comparison with a two-valve six-cylinder engine. The increase in the compression ratio stems from the fact that the combustion chamber becomes more compact. The increase in compression ratio from 9.0 to 10.0 leads to a two percent increase in the overall economy of the vehicle.

US D.O.E.
http://www.osti.gov/energycitations/...sti_id=5543681

The multi-valve four stroke cycle engine design trend is toward increased engine power and higher fuel efficiency. While a four-valve system is the most common direction, problems occur when the valve area is widened by increasing the cylinder bore for a higher engine output. The layout for four larger valves causes the combustion chamber shape to flatten and the combustion time period to increase. In pursuit of the optimum multi-valve engine we have studied four, five, six and seven-valve per cylinder design. Performance targets and design constraints led toward the successful five-valve engine technology.

Chevron
http://www.chevron.com/products/prod.../fuel_economy/
Increasing the number of valves provides other fuel economy benefits: "...the greater valve area...reduces pumping losses, and the more compact combustion chamber geometry and central spark plug location allow an increase in compression ratio."


Companies are getting beat up on FE and emission today...and the U.S. customer still wants performance. So there is one reason a company would still produce a 2V today: cost.

RLSH700

Yes, as a matter of fact there still are. Ford still makes a 2 valve version of the Modular engine, not to mention the 2 valve versions I have already made a reference to are still related. I know there are 4 valve pushrods, but that is mostly in the diesel market. These pushrod models are 2 valve, not to mention the long list of 2 valve OHC models I have listed. Every single one had better fuel efficiency than 4 valve engines

There is a simple problem with trying to say that the Europeans know how to favor fuel economy when all the ones offered over here have much worse fuel economy no matter what the engine size is. I don't care whether or not the Japanese and Europeans make 2 valve vehicles or not. That's their decision.

My point with the 6 liter engine reference is that there is simply not an 4 valve V8 with a displacement anywhere close to that engine's that can match its fuel economy; therefore, the 2 valve design is more fuel efficient.

The problem with those references is that there is no real-world evidence that this is infact true. Just because a book says it does not prove that it is infact accurate. I have looked all over the place and there is no evidence that when a switch over is done that the fuel economy increases unless the engine did not breathe well in the first place. Sometimes the efficiency could be a reference to getting better engine output per displacement, but then the question comes up, why bother using 4 valves per cylinder when it costs a lot more, has a more peaky power characteristics, and gets worse fuel economy? When I'm buying a V8, I'll get a nice large displacement engine which costs less and take the better fuel economy any day over smaller displacement, higher cost, and worse fuel economy, and you know what, a good portion of the American public agrees with my point of view. The Hemi has been a major success, as has the LS line; meanwhile, Ford has to supercharge the Modular to get it to compete.